The present invention is directed to computer systems and in particular to the power-conservation systems that they employ.
In lap-top and similar portable computers, one of the most critical features is the computer's power consumption: the less power the computer requires, the longer it can be used without recharging its batteries. In addition to expending a great deal of effort in reducing the power that various components draw when they are operating, therefore, workers in this art have additionally provided their computer systems with power-down circuitry, which turns off parts of the computer system when they are not needed. In U.S. Pat. No. 5,708,819 to Dunnihoo, for instance, a computer system's input-output controller removes power from the keyboard, floppy-disc controller, etc., when they are not in use. Similarly, U.S. Pat. No. 5,710,929 to Fung includes a power-control circuit that causes various of a computer's components to assume power-on, doze, sleep, suspend, and off states. By monitoring an input/output bus for various address ranges, it determines which states the various components should assume. And various network computer systems disclosed in U.S. Pat. No. 5,692,197 to Narad et al. determine when to enter respective power-down states, from which they may "wake" in response to various external signals.
While all of these approaches do serve the purpose of limiting power use, the fact remains that portable-computer battery life in general remains shorter than users would prefer.